Natural Fertility Conditions Research Articles

Влияние элементов технологии возделывания на урожайность и водопотребление гороха сорта Премьер в богарных условиях

Purpose: to identify the optimal combination of the seeding rate of seeds and the background of fertilizers to achieve a high yield of a new peas Premier variety, as well as to study the peculiarities of water consumption of the crop under the soil and climatic conditions of Azov zone Rostov region. Materials and methods. The studies were carried out in Aksai district Rostov region in 2019–2020. The soil of the experimental site is represented by ordinary calcareous medium-thick light loamy chernozem on loess-like loam. The experiments used the Premier pea variety. Factor A: seeding rates (0.8 (control); 1.0; 1.2 million pcs/ha); factor B: fertilizer backgrounds (high – N30Р80K80; medium – N15Р40K40; control without fertilizers) were studied. During the field experiment, the generally accepted methods were used (B. A. Dospekhov, 1985; A. N. Kostyakov, 1961; A. F. Vadyunina, 1986). Results. When growing peas in rainfed conditions, the priority effect on grain yield is provided by the moisture supply of plants during the critical period of water consumption. In years with optimal (GTC = 1.37) and stressful (GTC = 0.22) conditions of this growing season, the difference in yield indicators reached 47.0–51.9 %. The change in the seeding density from 0.8 to 1.0 and 1.2 million pcs/ha contributed to an increase in the average grain yield under different nutritional backgrounds, respectively, by 21.3–25.0 and 34.0–40.5 % compared to control. The fertilizer rate N15Р40K40 increased the peas yield at different sowing densities by 16.0–21.2 %, and a high background (N30Р80K80) – by 38.6–42.2 % compared to natural fertility conditions. The best payback of fertilizers by an increase in yield was obtained in the variant with a high background of nutrition N30P80K80 and a seeding rate of 1.2 million units/ha – 3.32 kg/kg. Conclusions. The best average grain yield was ensured at the rates of fertilization N30P80K80 and seeding of seeds of 1.2 million units/ha, reaching 2.26 t/ha.

ОСОБЕННОСТИ БИОСИНТЕЗА СУХИХ ВЕЩЕСТВ РАЗЛИЧНЫМИ СОРТАМИ КАРТОФЕЛЯ НА ЛУГОВО-ЧЕРНОЗЕМНОЙ ПОЧВЕ ОМСКОГО ПРИИРТЫШЬЯ

The article presents the material on the study of the varietal specificity of potato plants (Alaya Zarya, Svitanok, Kormilets, Zekura and Rosara) in the synthesis of dry substances on meadow chernozem soil of Omsk Priirtyshe under conditions of natural fertility and the use of optimal fertilizer doses (N45P90). Field experiments were conducted in 2008-2010 on the experimental field of Omsk State University. Experiments are of two-factor. Repeatability is threefold. The scheme for planting potatoes 70 × 30 cm with tubers weighing 80-100 g. The size of the pilot plot is 9.6 m2, the pilot plot is 510 m2. Comparative starch content of potato of experimental varieties reflects a number: Svitanok (20.3%)> Alaya Zarya (19.4%) >> Kormilets (16.7%)> Zekura (15.9%)> Rosara (15.6%). Intensive accumulation of dry matter occurred in the tubers of the Svitanok variety both in conditions of natural fertility and on a fertilized background. The increase in dry substances by 2.4-5.4% of their initial content in tubers due to the application of fertilizers (N45P90) is established for the varieties of Alaya Zarya, Svitanok and Rosara. Thus, the correct selection of varieties and the use of fertilizers make it possible to obtain a potato crop with the expected quality indices for dry matter and starch.

Effects ofBRCA1andBRCA2mutations on female fertility

Women with BRCA1/2 mutations have a significantly higher lifetime risk of developing breast or ovarian cancer. We suggest that female mutation carriers may have improved fitness owing to enhanced fertility relative to non-carriers. Here we show that women who are carriers of BRCA1/2 mutations living in natural fertility conditions have excess fertility as well as excess post-reproductive mortality in relation to controls. Individuals who tested positive for BRCA1/2 mutations who linked into multi-generational pedigrees within the Utah Population Database were used to identify putative obligate carriers. We find that women born before 1930 who are mutation carriers have significantly more children than controls and have excess post-reproductive mortality risks. They also have shorter birth intervals and end child-bearing later than controls. For contemporary women tested directly for BRCA1/2 mutations, an era when modern contraceptives are available, differences in fertility and mortality persist but are attenuated. Our findings suggest the need to re-examine the wider role played by BRCA1/2 mutations. Elevated fertility of female mutation carriers indicates that they are more fecund despite their elevated post-reproductive mortality risks.

Familial Aggregation of Survival and Late Female Reproduction

Women giving birth at advanced reproductive ages in natural fertility conditions have been shown to have superior postmenopausal longevity. It is unknown whether improved survival is more likely among relatives of late-fertile women. This study compares survival past age 50 of men with and without a late-fertile sister in two populations: Utahns born in 1800-1869 identified from the Utah Population Database and Québec residents born in 1670-1750 identified from the Programme de recherche en démographie historique. Male survival was greater for those with, rather than without, a sister reproducing after age 45, particularly among men with at least three sisters (Utah rate ratio [RR] = .801, 95% CI = 0.687-0.940; Quebec RR = .786, 95% CI = 0.664-0.931). Survival of wives was unaffected by whether their husbands had a late-fertile sister, suggesting a weak influence of unmeasured socioenvironmental factors. These results support the hypothesis that late female fertility and slow somatic aging may be promoted by the same genetic variants.

Does reproduction decrease longevity in human beings?

According to the disposable soma theory, a cost for reproduction could exist in human beings and other species and, thus, longevity could decrease when women have a higher number of children. The purpose of this article is to review the evidence in populations living or not living under natural fertility conditions, i.e. when fertility is near its biological maximum. The results indicate that in natural fertility conditions longevity does not decrease when the number of children increases but, in modern populations, mortality could slightly increase when women have more than ca 5 children. Complete data for these modern cohorts will tell us, one day, whether these results are still observed when the variable of interest is longevity and not only mortality.

Detecting Stopping and Spacing Behaviour in Historical Demography. A Critical Review of Methods

Couples who have started to reproduce and subsequently want to limit their fertility can follow two strategies: birth spacing or stopping. Spacing consists of increasing the intervals between successive births, while the stopping strategy attempts to prevent further reproduction altogether after the maximum desired number of children has been reached (Knodel, 1987; Okun, 1995).It is widely accepted among scholars that stopping has played the major role in the European historical fertility transition. This article contributes to the reopened debate about the role of spacing before and during the fertility transition (see Okun, 1995: Hionidou. 1998; Friedlander, Okun and Segal, 1999: Fisher, 2000; Clcgg. 2001). First, it will show how historical research on the fertility transition has been methodologically incapable of detecting intentional spacing behaviour in a convincing manner. secondly, it makes suggestions about the kind of methods to be used in future historical demographic research in order to assess the role of spacing.I. Commonly used methods for detecting stopping and spacingDuring the past decades, several attempts have been made to develop methods for detecting birth spacing in historical fertility data. Most attempts have not been entirely convincing. Yet, even if one assumes that spacing has not demonstrably played an important role in the European fertility transition, there is no hard evidence to the contrary either.Another index of fertility control that has often been used is the mother's age at last childbearing. Although a declining age has generally been interpreted as reflecting stopping behaviour, increased spacing has been shown to reduce age at last birth as well. There has been some controversy regarding the magnitude of that effect (see Knodel, 1987; Anderton, 1989; and the response by McDonald and Knodel, 1989), but simulations have shown that reductions in the mean age at last birth cannot be interpreted uncritically as a sign of stopping behaviour only (Okun, 1995). The same holds for an increase in the length of the last closed birth interval, which has been interpreted as evidence of failed attempts to stop childbearing. However, increased spacing affects all birth intervals, including the last. Since both forms of fertility regulation inflate the ultimate closed interval, research cannot differentiate between stopping and spacing by examining changes in the length of this interval (Okun, 1995).The main point to be made in the following discussion is that the lack of conclusive evidence in favour of or against spacing behaviour is also a consequence of the fact that many historical demographic analyses are carried out at a highly aggregated level. The next paragraphs investigate the consequences of such aggregations on different measures of spacing and stopping.1. Parity progression schedulesA well-known, more elaborate method for detecting fertilityinhibiting behaviour consists of investigating birth intervals as a function of the final number of children born in completed fertility histories (Knodel, 1987; Anderton and Bean, 1985). Some features of the pattern of birth intervals by final parity are true under conditions of natural fertility. First, the length of the intervals is negatively related to the final number of children born. Couples that reach a higher family size have on average shorter birth intervals. Second, within each final parity group, the length of the intervals increases with parity; the interval between the first and the second child is on average shorter than the one between the second and the third, and so on. This is basically a result of decreasing fecundity. Finally, the increase in length between the penultimate and the ultimate interval is greater than the increase between successive intervals at lower parities. This is expected when couples try to stop childbearing but holds as well under conditions of natural fertility. …

Marriage season, promptness of successful pregnancy and first-born sex ratio in a historical natural fertility population--evidence for sex-dependent early pregnancy loss?

We investigated population-based vital records of the seventeenth and eighteenth century French Canadian population to assess the effects of marriage season on the outcome of the first births under natural fertility conditions (n = 21,698 marriages). Promptness of the first successful conception after marriage differed according to marriage season; the proportion of marriages with a marriage-first birth interval of 8.0-10.0 months was lowest (34%) for marriages in August-October (P = 0.001). Although the male/female sex ratio of the babies born with an interval of 8.0-10.0 months was generally higher (1.10) than those with an interval of 10.0-24.0 months (1.05), the marriages in August-October resulted in a significantly reduced sex ratio (0.96) among only the prompt conceptions (P = 0.026). We discuss whether this seasonal reduction of the sex ratio could be partly explained by a clustered pregnancy loss of male zygotes in early pregnancy.

Slow twin conception at first birth and subsequent maternal twin proneness in a natural fertility population.

To study whether apparently more fecund women having delivered twins at first birth have traits of higher twin-proneness, we performed a retrospective cohort study on population-based historical vital records of the 17-18th century French Canadian immigrants and their descendants under natural fertility conditions. Among 24896 mothers who had at least one child, 248 had twin maternities at their first birth (twinning rate = 1.0%). Among 21508 mothers with a valid marriage-first birth interval, twinning rate was 0.97% among prompt conceptions (7.0-11.0 months), with a particularly high rate at the interval of 7.0-8.0 months (2.2%). Marriages in August-October resulted in a higher twinning rate particularly for the slow conceptions than those in the other seasons. Promptly-conceived mothers of twins at the first delivery may seem to have higher fecundity, but subsequent births from these mothers (n = 88) show a lower twinning rate (1.7%) particularly at younger maternal age than from the other mothers who had slowly conceived twins at their first birth (n = 112). The latter show a 4.5% twinning rate as a whole among their second or later births. So-called twin-proneness of a mother, whether genetic or acquired, was not connected to higher conception rate of twin's mothers immediately after marriage. Reduced fecundity, which may have been imposed by some environmental factors, could raise the chance of twinning.

Public policy and the total fertility rate: cross-sectional evidence from the LDCs

A framework developed by Easterlin for the analysis of fertility in developing societies is modified and then tested using a sample of 65 less-developed countries. The focus is on assessing the impact of public policy on the national fertility rate. Public policy is reflected in the average levels of education and health in the population and in the condition of the national family planning program. To test for threshold effects with respect to socioeconomic development, the sample is divided on the basis of the infant mortality rate. Fertility rates in those nations characterized by high infant mortality are likely to be determined more by conditions of natural fertility. Those nations with lower infant mortality, and hence greater socioeconomic development, are more likely to exhibit deliberate fertility control. The results of the regression analysis do suggest that different factors influence the national fertility rate depending upon the stage of development. For the least-developed nations, the secondary school enrollment rate, an indicator of the extent of economic mobility, and the ratio of school age children to teachers, a proxy for the national commitment to human capital formation, are important. For the more advanced of the LDCs, adult literacy and the infant mortality rate seem to predominate. For all the developing nations, however, the results confirm the importance of strong family planning programs. The paper concludes with a discussion of the policy implications of the research.

The Shift from Natural to Controlled Fertility: A Cross-Sectional Analysis of Ten Indian States

This study investigates the causes of the transition from natural to controlled fertility in India by comparing couples who have ever used contraception with those who remained under natural fertility conditions. Using sample study data this paper considers the relative effects of the factors involved in the shift to controlled fertility among ten early-transitional Indian States in 1970. The results indicate that it is primarily improvements in child mortality and its effects through intervening factors that account for the transition. The implication is that the success of a family planning program is largely a function of improvements in child health.

Effects of cyclic spouse separation on conception times

The lengthening of conceptive delays under conditions of natural fertility by cyclic spouse separation is investigated as a problem in renewal processes. Separations are “complete” if they reduce the conditional monthly probability of conception, or fecundability, to zero, and “incomplete” if they merely reduce it, from f to r say. Earlier work respecting cyclic separation by Menken (1979) is extended with formulas for the mean and variance of conceptive delays conditional on T, the ordinal month of the cycle of separation and nonseparation when the woman passes from anovulation into the fecundable state. A simple expression relating fecundabilities f and r and the conditional proportions P s ( T) and P s -( T) conceiving during separation and nonseparation is obtained.

Some Effects of Spouse Separation on Fertility

Simple probability models incorporating an approximation first demonstrated by Menken (1979) are used to study births averted by two classes of temporary spouse separation, single and cyclic, under conditions of natural fertility. For either class of spouse separation, births averted increases disproportionately with longer separation. For a given length of separation, births prevented are more sensitive to change in length of anovulation than to change in level of natural fecundability or risk of spontaneous abortion. In addition, by means of the macrosimulation model REPMOD (Bongaarts, 1977), it is shown that the fertility impact of temporary spouse separation tends to decrease as couples age.

Mormon Demographic History II: The Family Life Cycle and Natural Fertility

The concept of the family life-cycle has been central to a substantial body of literature in both demography and family history.1 Because the information necessary for a full description of the family life-cycle is often difficult to obtain in most of the studies made, twentieth-century perioddata have been used. Glick has provided a somewhat longer time series with his description of the life-cycle of the American family beginning with cohorts born during the latter part of the nineteenth century, although he was forced to use a combination of data sets and various estimation techniques.2 Even with the longer time series generated by Glick, it is fair to say that the portrait of the American family life-cycle which begins with cohorts of women born during the 1880s reflects a 'modern' pattern. This modern pattern emerges from an analysis of a population in which the life-cycle was strongly influenced by declining and controlled fertility, improving levels of infant survival and increasing parental life expectancy. Evidence of the nature of the family life-cycle in the United States under earlier and very different, demographic conditions is not in general available.' It is difficult to estimate patterns of change in the family life-cycle for the entire American population during the nineteenth century, but it is feasible to secure estimates for segments of the American population. In this paper, for example, we shall deal largely with a frontier population. It is also a population which is unique in its high level of fertility, consequently providing us with an opportunity to examine the nature of the life-cycle under conditions of natural fertility. This paper is intended to achieve the following specific purposes: to extend the study of the family lifecycle to selected birth cohorts born in the United States during the nineteenth century (1800-69), arid to examine the features of the family life-cycle under conditions of high natural fertility.

The Transition from Natural to Controlled Fertility in Taiwan: A Cross-Sectional Analysis of Demand and Supply Factors

Three factors are usually proposed as inducing the transition from natural to regulated fertility. Fertility regulation may occur when the demand for children is reduced; when general attitudes toward fertility regulaton become positive; and, finally, when such factors as infant and child survival prospects and natural fertility conditions improve. Applying the Easterlin framework for fertility determination, this paper considers the effect of these factors in the shift from natural to regulated fertility in Taiwan in 1965. Cross-sectional data for continuously married women aged 35-44 are used. The results indicate that, at the initial stages of the fertility transition, it is primarily an increase in the potential output of surviving children and a decline in the subjective costs associated with fertility regulation, rahter than a decline in desired fertility, that distinguish the natural fertility subpopulation from the regulating subpopulation.